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Orbital have been developing their stratified combustion process (Orbital Combustion Process OCP) for direct injection gasoline engines over the last 15 years, with successful production releases of the system in both the marine and automotive 2-stroke applications in 1996. This paper discusses how the same basic qualities of the air-assist fuel system and combustion process have been applied to automotive 4-stroke engines. The inherent qualities of the air- assist fuel system in combination with careful design of the combustion chamber has enabled high charge stratification with late injection timings and very stable combustion over a wide range of operating conditions. Experimental test data from a 4-cylinder, 16 valve 4-stroke development engine demonstrates the ability of this low pressure system to operate at very lean air/fuel ratios, with part load fuel economy improvements of up to 34 % at an operating condition equivalent to a vehicle speed of 40 km/hr.